1. Field of the Invention
The present invention relates to ophthalmoscopy lens systems, particularly those which may be sterilized without component damage or optical degradation.
2. Description of Related Art
Various ophthalmoscopy lens systems have been developed for use in the diagnosis and treatment of the eye. Many of these lens systems, particularly indirect ophthalmoscopy lens systems which create a real aerial image of structures within the eye, include a contact lens element which is placed directly on a patient's cornea. One particular type of indirect ophthalmoscopy lens systems is that used for vitreoretinal surgery. Such lens systems are described, for example, in U.S. Pat. No. 5,963,301 (which is incorporated herein by way of reference). Such lens systems are typically exposed to various bodily fluids during use, and therefore must be sterilized prior to each use.
Sterilization of ophthalmoscopy lens systems can be difficult and time consuming. In fact, many ophthalmoscopy lens systems can only be sterilized by specialized, time-consuming sterilization techniques, many of which will not be effective for certain microorganisms and other infectious agents. By way of example, “prions” are proteinaceous infectious agents which can cause transmissible degenerative encephalopathies such as Creutzfeldt-Jakob disease (“CJD”—a variant of which is the human version of “Mad Cow disease”). Prions tend to be more resistant to steam sterilization than conventional agents and are resistant to most sterilants typically used for sterilizing ophthalmoscopy lens systems. Recently, it has been reported that prions are susceptible to conventional autoclaving followed by a strong bleach solution or a solution of sodium hydroxide. Such a sterilization process will denature the prions. However, this technique cannot be employed with conventional ophthalmoscopy lens systems, particularly vitreoretinal lens systems such as those described in U.S. Pat. No. 5,963,301. Not only will the bleach solution damage the plastic contact lens element and other components, liquid will enter the air space between the contact lens element and the imaging lens.
In the past, various techniques have been used in an attempt to seal ophthalmoscopy lens systems. For example, various types of glue and other sealants have been positioned between lens elements and the frame. However, glues will eventually decompose and will never fully seal a lens assembly, thereby resulting in condensation on the interior of the lens which renders the lens system useless. Autoclaving will also cause degradation of glues.
Although some prior art ophthalmoscopy lens systems comprising a contact lens element and one or more imaging lens elements can be dissembled for sterilization purposes, some of the materials used in manufacturing the various elements of such lens systems are such that they must be sterilized using ethylene oxide. Such a sterilization process can take many hours to complete, and is much more expensive than other sterilants such as bleach. Sterilizing lens systems using a bleach solution (such as sodium hypochlorite), even if preceded by autoclaving, is much faster than sterilization using ethylene oxide. The time for sterilization can be further decreased if the ophthalmoscopy lens systems does not need to be disassembled prior to sterilization. Disassembling the lens prior to sterilization is time-consuming, and it is difficult to ensure that all moisture has been eliminated from the lens system upon re-assembly.